1. Field of the Invention
The present invention relates to a card type optical transceiver module which is optimum for connecting an optical communication line and a terminal such as a personal computer.
2. Description of the Related Art
Recently, as an optical transceiver module for use in the optical access system, an optical transceiver module having a single-core bi-directional transmission is mainly applied in order to miniaturize and to lower the price. The single-core bi-directional transmission means to perform a transmission and a reception function via a single optical fiber.
Especially, in the case of an optical access system using the Point to Point method, which connects a subscriber and a station of an optical line one to one, one subscriber exclusively uses one line system. Therefore, it is strongly required to lower the price of the optical transceiver module. Further, as optical fibers have come into wide use in the subscriber area, the station needs to accommodate a number of optical transceiver modules corresponding to the number of subscribers. Consequently, the requirement for miniaturizing optical transceiver modules is increased. Further, at the station accommodating a number of optical transceiver modules, an optical receptacle configuration which provides easy handling of optical fibers and a plug-in configuration capable of active insertion/extraction which provides easy exchanging in operation are also required.
Referring to FIGS. 14(a), 14(b) and 14(c), a conventional optical transceiver module 80 has such a configuration that the necessary components are mounted on a printed wiring board 85 using both the front and the back surfaces. On the front surface of the printed wiring board 85, a photoelectric component module 82 having a photoelectric component (not shown) to which an optical fiber 81 is connected, and an electronic component 84 are mounted. In the both edges of the printed wiring board 85, a group of pins 83, which are to be connected to an electronic device (not shown), are provided penetrating from the front surface to the back surface. The printed wiring board 85 on which the necessary components are mounted, is incorporated in a housing 86. An optical fiber 81 is drawn out from the front of the housing 86, and the group of pins 83 are drawn out from the under surface of the housing 86 in a downward direction. As shown in FIGS. 14(a) to 14(c), various electronic components are also mounted on the back surface of the printed wiring board 85.
Optical signals input from the optical fiber 81 are converted into electrical signals at the photoelectric component in the photoelectric component module 82, and are output to an electronic device (terminal) such as a personal computer via the group of pins 83. Electrical signals input from the group of pins 83 are converted into optical signals at the photoelectric component in the photoelectric component module 82, and output to an optical line via the optical fiber 81. The electronic component 84 may be an IC or a chip component, which performs processing of the electrical signals, controlling driving of the photoelectric component module 82, and the like.
As described above, the conventional optical transceiver module 80 has such a configuration that the electronic components and the like are mounted on the printed wiring board 85 using both the front and the back surfaces. Therefore, it is extremely difficult to thin the thickness of the housing 86. More specifically, the height of the photoelectric component module 82 may not be lowered to the height less than that of the photoelectric component to which the optical fiber 81 is connected. Turning to the printed wiring board 85, it mounts the electronic components and the like using both the front and the back surfaces, so that the height of the printed wiring board, to which the heights of the mounted components are added, may not be lowered beyond the limit. Accordingly, there is a limit in realizing a thin module by lowering the height of the housing 86.
As an idea to lower the height of the housing 86, it may be considered to mount the electronic components on one surface of the printed wiring board 85 in concentration. In this case, although it is possible to thin the housing 86, the horizontal size of the housing 86 corresponding to a lengthwise direction of the printed wiring board 85 is enlarged, which may not work as an effective solution.
Further, the group of pins 83 in the housing 86 extends from the bottom of the housing 86. Therefore, when the optical transceiver module 80 is to be mounted, a space for inserting/extracting the group of pins 83 must be kept in an up and down direction of the housing 86 (in a heightwise direction of the housing 86). This impedes to enhance the mounting density by closely mounting the optical transceiver module 80.